<!DOCTYPE html>
<body>
  The iframe below should show the text 'Here'<br>
  <iframe src="data:application/vnd.mozilla.xul+xml,&lt;window xmlns='http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul'&gt;&lt;label value='Here'/&gt;&lt;/window&gt;"
	  style="display: none"
	  onload="this.style.display = ''"></iframe>
</body>
